Does it happen often that someone who's invited for a state visit, first pays a working visit to that country and only later comes back for the state variety?

It won't be all that common, because only a head of state can make a state visit, while working visits are more often made by the head of government. Of the major developed nations, only in the US and France are the head of state and the head of government ordinarily the same person. The President of (for instance) Germany is head of state, but does not have a day-to-day involvement in government any more than King Willem-Alexander does in the Netherlands.

But as barbados says, working visits are commonplace events and wouldn't always even make the news. Much as most people in Belgium will know who she is, most people there probably don't know that Theresa May has made as many as twelve working visits to that country since she has been PM. If Donald Trump were not such a hate figure in Britain, I doubt there would have been much coverage of his brief visit to open a new embassy building.

On barbados' point, it may well be that the US did a crap deal in selling the Grosvenor Square building and moving to a new site near Battersea Power Station. But while that deal was signed off a few days after President Obama came to power and so is technically down to him, all the arrangements for that allegedly crap deal were made by the GWB administration, a point which President Trump has chosen not to make.

For the record, I don't know how long was left on the lease - but if the figure is anywhere near the £500million, then while not great (it is a huge chunk of prime real estate) it's not a crap deal. My point was more the location of the new building - on that he is correct, Nine Elms really is a shit hole.

Although casting my mind back to when it was my job to know such a thing, IIRC it was George Bush that put the wheels in motion, but not the one you are thinking of. It was during the time he was VP and attempts were made to purchase the freehold. At that time, the going rate was North, and most of south Carolina. That would imply that with around 900 years left on the lease, £500million is a snip

Presumably the freeholder of the Grosvenor Square building is the Duke of Westminster.

He is certainly the freeholder of Macdonald House, the former Canadian High Commission building the other side of Grosvenor Square. That building housed the US Embassy until 1960, and in 1961 the Dominion of Canada bought the lease off the United States of America.

The price was not made public, but Westminster reset the lease to 999 years when the transaction happened. He did the same thing again when Canada sold the lease on to an Indian company in 2014 for CDN 530 million. (Globe and Mail)

It seems likely that he again reset the lease to 999 years when the USA sold the lease on its soon-to-be former embassy to the Qatar Investment Authority. It's a bigger building than Macdonald House so it's no surprise that it's of higher value, but I discover at least one reason why the Americans have done a good deal.

Between the price being agreed and Qatar signing the check, the building was Listed. That usually reduces the value, and it has been explicitly stated that the listing includes the giant eagle, so Qatar can't take it down. Qatar's plan is to turn the building into an hotel, but such ostentatious Americana may not sit well with all of the rich Arabs it presumably hopes to have as residents there.

You were scared of me - a wee Scottish woman with a square of Lino and a sharpie pen - I spoke more truth in four words than you have in your entire occupation of the White House - now stay away you shitbag

Presumably the freeholder of the Grosvenor Square building is the Duke of Westminster.

Series H, episode 13 "Holidays" includes the story that the Duke once had a meeting with his tenant in which the State Department asked how much it would cost to buy out the freehold of the embassy. The Duke's response was that no money need change hands, but he would like them to return some of his family's property that was confiscated during the war of independence. When asked exactly what that property was, his response was "Virginia".

Yes but this is Mueller's investigation and he has subpoenaed him to appear in front of a grand jury, executive privilege not usable there. Hence the deal, which means he wont have to appear in front of the grand jury, for now at least.